I’m a longtime fan of investing for retirement in broad-based equity index funds. So is Warren Buffett, the greatest stock picker of the modern era, perhaps of all time.

Yes, Buffett himself takes large positions in a relatively small number of companies. But it’s an investment approach that takes time and discipline, which is why he doesn’t recommend it for the typical person who can’t make it a full-time job.

Why not hire investment pros to do the investing for you? To put it bluntly, most of them charge too much.

The big attraction of index funds is low fees — a fraction of the levy for actively managed mutual funds.

“Over the years, I’ve often been asked for investment advice, and in the process of answering I’ve learned a good deal about human behavior,” Buffett writes in his latest annual report. “My regular recommendation has been a low-cost S&P 500 index fund.”

With an index fund you will do as well as the market index, say, the S&P 500 or the Russell 3000, minus a razor thin fee. According to data compiled by S&P, more than 90 percent of active managers underperformed their benchmark indexes over a 15-year period.

Of course, equity managers sometimes beat the market. But few manage the feat consistently, year after year.

The latest evidence favoring an index fund investing approach comes from a famous bet Buffett made a decade ago. He wagered $500,000 that over a 10-year period — Jan. 1, 2008, to Dec. 31, 2017 — the S&P 500 index would outperform a portfolio of hedge funds. Performance would be measured net of fees, costs and all expenses. Ted Seides of asset manager Protégé Partners took up the challenge. Five funds-of-funds were chosen and their averaged results were to be compared to the performance of the Vanguard S&P 500 index fund.

We’re not at the end of the year yet, but Buffett’s index investment is so far ahead that Seides conceded the match. “For all intents and purposes, the game is over,” Seides wrote in a Bloomberg post. “I lost.”

But I haven’t found the latest round of criticisms convincing. The outcome of Buffett’s bet reinforces two investing lessons for the average investor in a 401(k) and 403(b) retirement savings world. First, fees matter. Second, keep your finances and investment strategy simple.